JP3042892B2 - Microfibrillated cellulose and primary wall plant pulp, especially its production from beet pulp - Google Patents

Abstract

A microfibrillated cellulose contains at least 80% of prim. walls, and is charged with carboxylic acids.

Description

The present invention relates to a novel soft tissue cellulose and a method for producing the same. More particularly, the present invention relates to a novel microfibrillated cellulose and a method for its production from primary wall vegetable pulp, especially beet pulp after extraction of saccharose.

Cellulose is used as a thickener to stabilize dispersions, emulsions and suspensions for low calorie foods, low fat or low cholesterol foods, etc., paints, paper, textiles, agriculture Industrial use such as cosmetics, cosmetics, etc .;-pharmaceutical use such as excipients for drugs, sedimentation regulators, ointment or cream carriers, intestinal transport agents, etc .; .

To date, all known celluloses have had drawbacks.

Weyerhaeuser WO 93/11182 describes bacterial cellulose having a network structure. Apart from being very expensive, such bacterial cellulose can cause contamination problems in food applications.

ITT INDUSTRIESFR-A-2 472 628 describes a microfibrillated cellulose substantially constituted by secondary walls obtained from wood pulp. Once dehydrated, such cellulose is not easily absorbed by the suspension. This creates considerable storage and transport problems due to the fact that the suspension has a maximum cellulose content of about 4%.

Tried to solve the shortcomings, ITT INDUSTRIES FR-
A-0 120 471 discloses redispersible dried secondary wall (as it is obtained from wood pulp) microfibrillation characterized by the presence of additives that prevent the formation of hydrogen bonds between cellulose fibrils. Cellulose is described. The amount of additives is considerable (at least 50% by weight, preferably at least the same amount as the cellulose). Additives are, for example, polyhydroxylated compounds, for example sugars or glycols containing 5 to 6 carbon atoms, borates or alkali phosphates, aprotic solvents, amines or quaternary ammonium compounds.
Aside from the fact that the name "cellulose" has been incorrectly designated for products that are at most half the cellulose, this "cellulose" is expensive and unsuitable for all uses. Moreover, without the addition of additives, the cellulose can only recover from 2% of its initial viscosity to a maximum of 20% after drying. Maintaining viscosity requires the presence of additives in amounts that are substantially the same as the amount of cellulose (by weight).

Weibel EP-A-0 102 829 describes a method for simultaneous isolation of the cellulose and hemicellulose components of beet pulp. However, the above-cited FR-A-247
As with 2628, once dehydrated, the resulting soft tissue cellulose is not easily absorbed again into the suspension, causing the same storage and transport problems.

Furthermore, economical utilization of plant residues, especially beet pulp, is of great industrial importance.

One object of the present invention is to provide a microfibrillated cellulose that can be absorbed into a suspension after dehydration without the addition of additives.

Another object of the present invention is to provide a microfibrillated cellulose which regains almost all of its initial viscosity after drying without the addition of additives.

Yet another object of the present invention is to provide a method for producing cellulose by economical utilization of primary wall plant residues, especially beet pulp.

 The present invention achieves all three of these objectives.

Further objects and advantages of the present invention will become apparent from the following description.

In general, natural cellulose is always in microfibrillated form, and these microfibrils are associated to a large or small extent to form fibers, walls and membranes. Each cellulose microfibril is composed of a precise assembly of parallel cellulose chains obtained by the process by which cellulose is biosynthesized. Cellulose microfibrils are generally considered to contain only a few defects along their axis. Their mechanical properties are close to the theoretical mechanical properties of cellulose: tenacity on the order of 130 GPa and fracture toughness on the order of 13 GPa. Thus, cellulose microfibrils are important if they can be dissociated and modified.

Cellulose microfibrils are usually highly associated in walls or fibers. The microfibrils in the secondary wall are organized into highly oriented layers, which form fibers that cannot be dissociated. The microfibrils in the primary wall are deposited in an unstructured manner. Soft tissue is a typical example of primary wall tissue. It is difficult, if not impossible, to separate secondary wall cellulose microfibrils without damaging them, but dissociating primary wall microfibrils is not only due to their loose organization. Easier, because the interstitial polysaccharides (which are usually charged) make up a large percentage of these walls.

Examples of soft tissue include beet pulp, citrus fruits (lemon,
Oranges, grapefruit) and most fruits and vegetables. An example of a secondary wall plant is wood.

The primary wall microfibrils can be defibrated using a mechanical shearing operation to break down the secondary wall fibers to produce microfibrils. In other words, microfibrils are obtained from secondary walls by breaking up the initial fibers.

Thus, primary wall cellulose is a material with great potential.

 The present invention is described with reference to beet pulp.

Beet pulp is mainly composed of parenchyma and thus primary wall cells.

The composition (by weight) of the solid beet pulp can vary depending on the source of the pulp and the culture conditions. Generally, the pulp is -15% to 30% cellulose, -12% to 30% pectin -12% to 30% hemicellulose, -2% to 6% protein, -2% to 6% inorganic material,- Contains 2% to 6% lignin, tannins, polyphenols and ferulic acid esters.

The treatment of beet pulp to isolate cellulose from parenchyma cells has already been proposed. EP-A quoted earlier
-0 102 829 relates to such a process, wherein the beet pulp is acidified (pH <4.5) or basic (pH>1);
0.0) suspending the suspension at a temperature above 125 ° C. (0.5 MPa), keeping the suspension at a temperature above 125 ° C. for a period of 15 seconds to 360 seconds, -Subjecting the heated suspension to mechanical shearing in a tubular reactor, followed by rapid depressurization through a small orifice to a zone at atmospheric pressure;-filtering the suspension and removing soft tissue cellulose. The insoluble fraction and the soluble fraction containing hemicellulose (filtrate) are collected, and the cellulose fraction is treated by bleaching with sodium hypochlorite and mechanical defibrillation to form soft tissue cellulose constituted by cell wall fragments. It describes producing a paste.

As described above, once dehydrated, EP-A-0 102 82
Cellulose obtained using the method of 9 cannot be readily absorbed into the suspension.

The present invention provides the following steps: (a) acidic or basic hydrolysis of pulp to partially extract pectin and hemicellulose; (b) a step of recovering a solid residue from the suspension from step (a); (c) Performing a second extraction of the residue of the cellulosic material from step (b) under alkaline conditions (this step is necessary if step (a) is acidic and
(D is optional if is basic), (d) optionally, a step of recovering the cellulose material residue by separating the suspension from step (c), (e) step (b) or step ( washing the residue from d), (f) optionally bleaching the cellulose material from step (e), (g) recovering the cellulose material by separating the suspension from step (f) (H) diluting the cellulosic material from step (g) in water to obtain 2% to 10% dry matter; (i) homogenizing the cell suspension from step (h) A method for producing microfibrillated cellulose from primary wall plant pulp, especially beet pulp after saccharose extraction, comprising: (j) performing step (a) at about 60 ° C to 100 ° C, preferably at about 70 ° C.
(Jj) performing at least one alkali extraction step (a) and (c) on the cellulosic material, wherein said alkali extraction is selected from a base, preferably caustic soda and caustic potash. (Jjj) mixing or milling or high mechanical shearing operations followed by homogenizing step (i), followed by a high mechanical shearing operation, wherein the concentration is less than about 9% by weight, preferably about 1% to 6% by weight. Microfibrillated cellulose characterized by passing the suspension through a small diameter orifice of the cell suspension and subjecting the suspension to a pressure drop of at least 20 MPa and a high shear action followed by a high speed deceleration impact. A manufacturing method is provided.

Conditions (j), (jj) and (jjj) are new. It will be shown below that they can give rise to unique structural, morphological, chemical and rheological properties.

In step (a), the term "pulp" means wet, dehydrated, silo-prepared, or partially depectilized pulp.

The extraction step (a) can be performed in an acidic medium or a basic medium.

For acidic extraction, the pulp is suspended in water for a few minutes to homogenize the suspension acidified with a concentrated solution of an acid, for example hydrochloric acid or sulfuric acid, at a pH of 1-3, preferably 1.5-2.5. .

For basic extraction, the pulp is added to an alkaline solution of a base, such as caustic soda or caustic potash, at a concentration of less than 9% by weight, preferably less than 6% by weight, more particularly 1% to 2% by weight. Small amounts of water-soluble antioxidants, such as sodium sulfite Na ₂ SO _3, can be added to limit the cellulose oxidation reaction.

According to the present invention, step (a) is performed at a "moderate" temperature of about 60C to 100C, preferably about 70C to 95C, more preferably about 90C.
At a temperature of This is in contrast to the high temperatures (> 120 ° C.) used in the prior art. The duration of step (a) is from about 1 hour to about 4 hours. During step (a) of the present invention, partial hydrolysis occurs with release and solubilization of pectin and hemicellulose, while preserving the molecular weight of the cellulose.

In step (b), a solid residue is recovered from the suspension from step (a).

If the first extraction (a) is an acidic hydrolysis, a second extraction step (c) is required and is performed under basic conditions. When the first extraction step (a) is a basic hydrolysis, the second extraction step (c) is optional.

Thus, if necessary, the cellulose material residue from step (b) undergoes a second extraction step in step (c). This latter step is an alkaline extraction step.

Thus, the process of the invention always comprises at least one alkali extraction step.

According to the present invention, each alkali extraction step-that is, the optional alkali extraction step of step (c) and / or the extraction of step (a) (if it is basic)-is performed using a base. If necessary, the base is preferably selected from caustic soda and potassium caustic, the concentration of which is less than about 9% by weight, preferably about 1% to about 6% by weight.

Applicants have shown that performing each alkali extraction step using the conditions of the method of the invention avoids an irreversible transformation: cellulose I → cellulose II.

This transformation will destroy the microfibrillar structures required for certain properties of the products of the invention.

The duration of each alkali extraction step is from about 1 hour to about 4 hours, preferably about 2 hours.

In step (d), a solid residue is recovered from any step (c).

In step (e), the residue from step (b) or step (d) is washed with copious amounts of water to recover cellulosic residue.

According to the present invention, a certain percentage (%) of non-cellulosic acidic polysaccharides (pectin, hemicellulose) is retained on the surface of cellulose microfibrils which have the effect of preventing them from associating with each other. This proportion (%) of acid polysaccharide is generally less than about 30% by weight, preferably 5% by weight.
Is less than. Too much acid polysaccharide requires too long a homogenization period, but according to the invention, this ratio (%) must be greater than zero.

The cellulosic material of step (e) is then, in step (f),
For example, sodium chlorite, sodium hypochlorite,
If necessary, bleaching is carried out by a method known per se using 5 to 20% of a dry content of hydrogen peroxide or the like. Different concentrations are about
It may be used at a temperature between 18C and 80C, preferably between about 50C and 70C. The duration of step (f) is from about 1 hour to about 4 hours, preferably from about 1 hour to about 2 hours. Cellulosic materials containing from 85% to 95% by weight of cellulose are thus obtained.

In step (h), the suspension from step (e) may be bleached in step (f) if necessary,
Diluted to 1010% dry matter and then sent to step (i), which, according to the invention, is mixed or comminuted using high mechanical shearing operations, This is done by passing the suspension through a diameter orifice and subjecting the suspension to a pressure drop of at least 20 MPa and a high shear action followed by a high speed deceleration impact.

Mixing or milling may be accomplished in a device such as a Waring blender with a four-blade screw, or in a mixing mill or other type of grinder, such as a colloidal mill, for several minutes to about 1 hour under the following conditions. This is done by passage through a mixer or grinder over a period of time. The concentration of dry cellulosic material is 2% to 10% by weight
Range. During mixing or grinding, the suspension becomes hot. The receptacle preferably comprises a system of flexing ribs, whereby the liquid is moved back towards the screw blades in the center of the receptacle.

The homogenizing proper is advantageously carried out in a Menton-Gaulin type homogenizer, in which the suspension is subjected to a high-speed and high-pressure shear action on the impact ring in a narrow passage. The homogenization conditions are as follows. After mixing or grinding, the concentration of dry pulp in the suspension ranges from 2% to 10% by weight. The suspension is at 40 ° C to 120 ° C, preferably 8 ° C.
It is preferably introduced into the homogenizer after preheating to a temperature of 5 ° C to 95 ° C. The temperature of the homogenization operation is 95 ° C ~ 120
° C, preferably kept at 100 ° C or higher. In the homogenizer, the suspension is subjected to a pressure that is between 20 MPa and 100 MPa, preferably above 50 MPa.

Until a stable suspension is obtained, 1
It is homogenized in 2020 passes, preferably 2-5 passes.

Homogenization in the context of the present invention is based on the above-cited ITT INDUST
RIES patents FR-A-2 472 628 and EP-A-01
It should be noted that it has functions different from those of 20 471. In the method of the present invention, the function of the homogenization step is to defibrate the microfibrils without decomposing them, while in the above-mentioned ITT INDUSTRIES patent, the function of the step is to decompose the secondary wall fibers. To obtain microfibrils.

Following the homogenization operation of step (i), for example, SYLVERSO
High mechanical shearing operations are advantageously performed in N to Ultra Turrax equipment.

We have proved that the treatment is more effective at higher dry matter concentrations in the suspension to be homogenized and at higher homogenization temperatures. This means that the required number of passes decreases as the cellulose concentration increases. However, the viscosity of the suspension during processing, which is directly dependent on the concentration of the processed suspension, is a limiting factor. In fact, the device is not designed to operate with suspensions that are too viscous.

Applicants have demonstrated that a special valve exists for cell disruption that can reduce the number of passes. In addition, the number of passes can be determined by the water-soluble dispersing, suspending or thickening agents, such as carboxymethylcellulose, cellulose ethers, gelling polysaccharides (guar, carouba, alginate, carrageenan, xanthan and derivatives thereof). Is added to the suspension to be homogenized.

Beet pulp contains 4% to 6% inorganic compounds that are insoluble in water.

Significant (> 1 mm) pieces of soil residues and coarse particles are among the inorganic compounds present in beet pulp. Applicants have discovered calcium oxalate monohydrate and silica crystals in these insoluble inorganic compounds. Calcium oxalate monohydrate is commonly found inside cells that are localized near the vascular tract and the wood tract bundle. Calcium oxalate crystals are contained in certain cells and constitute a form of calcium storage in plants. The nature, amount and ratio of these inorganic substances can vary depending on the soil in which the plant is cultured, beet varieties, growing climate, and the like.

The presence of calcium oxalate crystals causes problems during homogenization because they are highly abrasive and it is preferred to eliminate them or at least significantly reduce their amount. The exclusion is carried out by treatment in an acidic medium, for example hydrochloric acid, for example by acid extraction as performed in step (a) (if the step is carried out under acidic conditions, of course), which comprises calcium oxalate. Converts hydrates to oxalic acid and calcium chloride, which are soluble in water.

Also, calcium oxalate can be eliminated by mechanical blending and screening. Applicants have blended and screened the dehydrated pulp prior to step (a) to determine that the concentration of residual minerals is between about 20 μm and 1000 μm, preferably 75 μm.
It has been demonstrated that the reduction can be achieved by retaining only those fractions having a particle size between μm and about 600 μm.

If the cellulose residue contains non-negligible amounts of free calcium oxalate crystals or calcium oxalate crystals inside the cells after basic extraction or bleaching, moderate grinding may be performed, for example, in a Walling blender mixer or other grinder. Performed wet to destroy cells, followed by filtration or screening with a suitable screen. The screen mesh can be readily determined by those skilled in the art, for example, depending on the degree of mixing or grinding, i.e., depending on the size of the resulting cell fragments and industrial feasibility, from 20 μm to 75 μm, for example, 75, 60 μm. ,
Up to 40, 20 μm mesh.

Yet another means of eliminating the calcium oxalate problem is
Performing an oxidation treatment associated with the bleaching treatment of step (f), for example, with ozone or hydrogen peroxide.

The bleaching step (f) can also be performed using ozone or hydrogen peroxide to eliminate calcium oxalate crystals.

Any means of eliminating or at least reducing the amount of calcium oxalate crystals may be combined with each other or used separately, as can be readily determined by the skilled person in each particular case.

The microfibrillated cellulose obtained using the method of the present invention is cellulose I.

The cellulose of the present invention contains at least about 80% primary walls and is charged with a carboxylic acid.

It is characterized by being microfibrillated and charged by galacturonic acid. The term "galacturonic acid" means a single galacturonic acid, its polymer and its salts.

More specifically, the cellulose of the present invention has at least about 85
% Of primary walls included.

The microfibrillated cellulose of the present invention is notable in that it can be absorbed into the suspension after dehydration.

15% to 50% of the microfibrillated cellulose of the present invention
Is the crystallinity of

It is constituted by microfibrils having a cross section of about 2 nm to about 4 nm.

The microfibrillated cellulose of the present invention forms a stable suspension of the liquid crystal type composed of nematic domains.

The microfibrillated cellulose of the present invention has the following beneficial properties: stable suspensions at a pH in the range from 2 to 12 and a temperature range from 0 ° C. to 100 ° C. with a minimum concentration of 0.2% and with a concentration of more than 1% It has a group of unique rheological properties that can be produced with the appearance of a gel.

The cellulose of the present invention behaves as a weak gel with 1% DM (dry matter) in water. In studying the viscous viscoelastic behavior of the product under vibration, G 'and G "should be stable in the frequency range, and G' = 5G" (G 'is the elastic component of the system and G " Is a viscous component.) It should be noted, for example, that xanthan does not behave as a gel.The viscosity of the cellulose of the present invention at 20 ° C. is much higher than that of xanthan at 20 ° C. And at 80-90 ° C equals the viscosity of xanthan.

With respect to the viscosity at 2% in water, the cellulose of the present invention has a viscosity equivalent to high viscosity CMC of the same concentration (about 20,000 mPa.s).
With a shear rate of 1.8s ^1- . The cellulose of the present invention has a viscosity which is much higher than that of xanthan (about 7000 mPa.s). 1.8% cellulose of the invention and 0.2% CM in water
The mixture of C has beneficial rheological properties as the solution reaches a viscosity greater than 25000 mPa.s.

The cellulose of the present invention is a rheofluidifying and chictropic substance.

-Unique physical and chemical properties in that the cellulose is mainly constituted by residual amounts of cellulose associated with pectin or hemicellulose which give rise to particular physical and chemical properties. The cellulose of the present invention is constituted by natural or cellulose type I microfibrils separated to a large or small extent.

-Very high chemical reactivity, very large accessible surface area,-excellent water retention capacity,-high suspending capacity,-thickening capacity, the cellulose of the present invention produced by the above method,
For example, precipitation with an alcohol, such as ethanol, isopropanol or other similar alcohols,
Freeze-thaw method, pressing by passage through a filter press (this is not available with other hydrocolloids, such as xanthan, CMC, etc.), filtration, dewatering, molecules larger than the pore size of the membrane used By dialysis against a hygroscopic solution having a size or by using any other method known to those skilled in the art for concentrating such suspensions, preferably about 50%
Can be concentrated to% dry matter.

Cellulose, directly from the process of the invention or after the concentration step, can be evaporated, dehydrated, dried at low humidity under controlled humidity,
High or low energy drying can be achieved by spray drying, drum drying, freeze drying or critical point drying, or any other method that allows the product to be obtained in its secondary state. Low temperature drying under controlled humidity is particularly advantageous in this regard because they are gentle and have low energy costs.

ITTT INDUSTRIES Patent EP 120 471 (where the microfibrillated structure can only recover from 2% up to 20% of its initial viscosity after drying without adding additives (p. 4, lines 38-42) In contrast, the celluloses according to the invention recover almost all of their initial viscosity after drying without the addition of additives.

Also, the celluloses of the present invention have beneficial film-forming and reinforcing properties.

The suspension of the microfibrils of the present invention is applied to a surface, for example,
When applied to a metal, glass, ceramic, etc. surface and dried, the microfibrils form a film on that surface.

The cellulose of the present invention, when applied in a thin layer, forms a film after dehydration. Film properties are measured by measuring a modified Young's Modulus (Ecor), which indicates the stiffness of the system. For example, Ecor is 2500 at 25% humidity
~ 3000 MPa.

Also, wet paper sheets can be treated during manufacture with the cellulose suspensions of the present invention, thus improving their physical properties, especially their tensile strength.

In the non-food field, there are many potential uses for the cellulose of the present invention.

-With respect to paints, it constitutes a good thickener in the aqueous phase and can replace, for example, hydroxy-propyl-cellulose;-its film-forming and reinforcing properties are for paints, paper, adhesive coatings, etc. Latex.

The incorporation of 1% to 15% microfibrillated cellulose in latex (and other water-soluble products) or thermoplastic compounds or cellulose acetate improves the modulus of elasticity and tensile strength after significant surface transformation.

-As a thickener that can be used in large water.

In the cosmetics and paramedical fields, the microfibrillated cellulose of the present invention constitutes a thickener that competes with carbopol or other thickeners used in these fields. This product has the advantage of being less tacky than other products, significantly improving the rinsing properties of the product,
Give it a more comfortable feel.

 In the papermaking industry, the following may be mentioned.

Using the reinforcing properties of microfibrillated cellulose by introducing it into the paper pulp; combining the thickening, reinforcing properties and film forming properties of microfibrillated cellulose for coating certain special papers. Made use. Also, the cellulose has beneficial barrier properties.

Also, the cellulose of the present invention can be attached to the surface of paper to improve its opacity and uniformity.

The cellulose of the present invention can be applied alone or with other compounds such as pigments and fillers, which are commonly used in the paper industry.

The reinforcing properties of cellulose will be used, for example, by introducing it into paper pulp.

In the food sector:-microfibrillated cellulose stabilizes emulsions and can act as a fragrance carrier, a gelling agent, in particular as a thickener.

-It can replace or synergize with other thickeners already used in the field, such as xanthan, CMC or microcrystalline cellulose.

Synergistic use is particularly important from an economic point of view. That means that significantly fewer products can be used to achieve the same effect.

Examples of applications of microfibrillated cellulose in the food sector are fat replacement, mayonnaise, salad dressings,
And generally all emulsions, ice creams, stir-fried cream, drinks, pastes that spread well,
Any type of thickener, such as dough or fermented dough, milk desserts, meat products, etc.

For the same rheological effect, the cellulose of the present invention is much cheaper than xanthan and bacterial cellulose.

The present invention is further described by the following non-limiting examples with reference to the drawings.

FIG. 1 is a light micrograph of individual parenchyma cells.

FIG. 2 is a transmission electron micrograph of natural cellulose (cellulose I).

FIG. 3 is a transmission electron micrograph of cellulose II.

FIG. 4 is a transmission electron micrograph of the cell wall before homogenization in a Gaulin homogenizer.

FIG. 5 is a transmission electron micrograph of the individual microfibrils after homogenization (6 passes) in a Gaulin homogenizer.

FIG. 6 is a transmission electron micrograph of the separate microfibrillation after homogenization (10 passes) in a Gaulin homogenizer.

Example 1: Purification of beet pulp Dehydrated pulp of beet harvested from the Nasandre region of France was absorbed into a suspension in deionized water. For good hydration, intermittent mixing was performed for 45 minutes using a Walling blender mixer equipped with a four blade screw. By adding a solution of H ₂ SO _4, it was acidified suspension to pH 2. The suspension was kept at room temperature (25 ° C) for 15 minutes with constant mechanical stirring and then heated to 80 ° C for 2 hours. The suspension was filtered with a metal screw and washed with plenty of water. The solid residue after washing was extracted with an alkaline solution. It was absorbed into the suspension in caustic soda solution at a concentration suitable to yield a final caustic soda concentration of 2% by weight and a dry% of 2.5% by weight (both relative to the total liquid). About 0.1% by weight of sodium bisulfite (Na ₂ SO ₃ ) based on the total liquid was added. The suspension was heated to 80 ° C. for 2 hours with constant mechanical stirring. After this treatment, it was filtered through a 0.6 mm sieve. Until a neutral filtrate is obtained
The solid residue was washed with water.

After washing, the solid residue is adjusted to pH with a mixture of caustic soda and acetic acid.
Sodium chlorite solution (NaClO ₂ ) buffered to 4.9 3.4
Absorbed in a 2.5% suspension in g /. The suspension was heated to 70 ° C. for 3 hours with constant mechanical stirring. It was then filtered through a stainless steel screen, then rinsed with water until a colorless filtrate was obtained. 3% by weight to 5%
A pale gray cellulose residue with a dry weight of% by weight was obtained by filtration under reduced pressure using a Buchner funnel.

The neutral sugar composition of the solid residue was determined by chemical analysis based on gas chromatography characterization of the alditol acetate obtained after acid hydrolysis of the polysaccharide, reduction of the sugar monomers and acetylation. The alditol acetate was identified using GC, and the sugar was measured using myo-inositol as an internal standard, taking into account each specific response factor of alditol. The chromatograph was a Hewlett-Packard 5890 equipped with a flame ionization detector coupled to a Hewlett-Packard 3395 integrator. SP 2
A 380 (0.53 mm x 25 m) column was used with U nitrogen as carrier gas.

Alditol acetate was eluted at the retention time characteristic of the column. Studies were performed to determine the response factors for each alditol acetate. Knowing the area and amount of the starting inositol, and then using the surface area of the peak for each alditol acetate, the corresponding amount of ose can be deduced to give the total mass of neutral sugar in the sample. The weight percent of each of the resulting neutral sugar monomers could be calculated. Glucose almost completely derived from the hydrolysis of cellulose,% of glucose
Thus gave an indication of the purity of the cellulose in the sample. Other neutral sugars are mainly xylose, galactose, mannose, arabinose and rhamnose,
An estimate of the amount of residual pectin and hexcellulose was given.

Chemical analysis of the resulting cellulose residue showed 85% glucose.

Example 2 Purification of Beet Pulp The entire series of treatments of Example 1 was repeated, with the addition of a second treatment with sodium chlorite identical to the first treatment after the sodium chlorite treatment and the corresponding rinsing step. This resulted in a white cellulose residue with a neutral sugar chemistry that changed little during the second bleaching step. Chemical analysis showed 86% glucose in the resulting cellulose residue.

Example 3: Purification of beet pulp Dehydrated pulp was absorbed into a suspension in deionized water and then acid hydrolyzed using the method described in Example 1. It was filtered and washed with water to eliminate dissolved pectin and hemicellulose. Then the solid residue was prepared according to Example 1
Extracted with alkaline solution using the method described in This alkali treatment was performed once more. The solid residue was washed with water until a neutral filtrate was obtained, followed by two consecutive bleaching steps using sodium chlorite and the method described in Example 1. Chemical analysis showed 89% glucose.

In Examples 1, 2 and 3, the larger the number of extraction steps,
The cellulose in the residue indicates that it is pure.

Example 4: Purification of beet pulp The pH of the suspension was adjusted to 2 by replacing the sulfuric acid solution with a hydrochloric acid solution.
The entire series of treatments of Example 1 was repeated.

Cellulose residue, as obtained in Example 3,
It contained 90% glucose.

Example 5: Purification of beet pulp Dehydrated pulp was absorbed into a suspension in deionized water. For good hydration, intermittent mixing was performed for 45 minutes using a Walling blender mixer equipped with a four blade screw. 2% by weight final concentration of caustic soda and 2.5% by weight
The suspension was made alkaline by the addition of caustic soda solution at a concentration suitable to obtain a% dry matter (both relative to the total liquid). About 0.1% by weight of sodium bisulfite (Na ₂ SO ₃ ) based on the total liquid was added. The suspension was heated to 80 ° C. for 2 hours with constant mechanical stirring. After this treatment, it was filtered through a 0.6 mm screen. The solid residue was washed with water until a neutral filtrate was obtained. This alkali treatment was performed once more. The solid residue was washed with water until a neutral filtrate was obtained, followed by two consecutive bleaching steps using sodium chlorite and the method described in Example 1.

 Chemical analysis showed 87% glucose.

Example 6: Purification of beet pulp Instead of the two treatments of Example 5, 3 with a suitable concentration of caustic soda to produce a final caustic soda concentration of 2% by weight
The entire series of treatments of Example 5 was performed using successive alkali treatments. The solid residue was washed with water until a neutral filtrate was obtained, followed by two successive bleaching steps with sodium chlorite using the method described in Example 1.

 Chemical analysis showed 92% glucose.

Example 7: Purification of beet pulp The treatment of Example 5 except that the two alkali treatments with caustic soda are replaced by two successive treatments with a caustic potash solution of a suitable concentration to produce a final caustic potash concentration of 2% by weight. The whole series was repeated. The solid residue was washed with water until a neutral filtrate was obtained, followed by two successive bleaching steps with sodium chlorite using the method described in Example 1. Caustic potash was used to obtain a cellulose residue with a purity similar to that obtained with caustic soda.

Example 8: Effect of caustic soda concentration Dehydrated pulp was absorbed into a suspension in deionized water by mixing in the same manner as described in Example 1. The resulting suspension was heated under reflux for 20 minutes and then filtered through a 0.6 mm screen. The solid residue is then absorbed into a suspension in a caustic soda solution at a concentration suitable to produce a final caustic soda concentration of 2% or 8% by weight and a dry matter content of 2.5% by weight (both relative to the total liquid). I let it. The suspension was magnetically stirred at 20 ° C. for 3 hours. After this treatment, it was filtered through a 0.6 mm screen and washed with water until a neutral filtrate was obtained.

After extraction, the percentage of glucose obtained for treatment with 2% or 8% caustic soda was as shown in Table I.

Thus, it can be seen that the use of concentrated caustic soda during the first alkali extraction step results in high purity cellulose.

Example 9: Effect of caustic soda concentration Dehydrated pulp was treated as in Example 6. The purified cellulose residue yielded a 4% paste after filtration under reduced pressure using a Buchner funnel, which was simultaneously processed in a similar manner in eight separate experiments. 2% by weight, 7% by weight,
9 wt%, 9.5 wt%, 10 wt%, 12 wt%, 14 wt%
And 50 ml of a 17% by weight caustic soda solution.
Added to 6g. The treatment was carried out at a temperature of T = 20 ° C. for 2 hours with constant magnetic stirring. After neutralization with hydrochloric acid and dialysis of these suspensions against distilled water, the residue was oven dried in a small receptacle at 50 ° C. to give a thin film of cellulose residue for each experiment.

In other experiments, droplets of the post-dialysis suspension were deposited on an electron microscope grid and then dried before testing.

X-ray studies have shown that films obtained from cellulose treated with 2% to 9% by weight of caustic soda diffract in the same manner as the starting cellulose. These are cellulose I (0.54%) having a degree of crystallinity of the order of 35%.
nm, 0.4 nm and 0.258 nm). In contrast, spectra characteristic of cellulose II were obtained for cellulose films treated with caustic soda at a concentration of 9.5% or more. It was particularly characterized by interference at 0.7 nm, 0.44 nm, 0.4 nm and 0.258 nm.

Electron microscopy examination demonstrated that the samples treated with 2% to 9% caustic soda were in the form of entangled, smooth cellulose microfabrics that could slide with each other (FIG. 2). In contrast, after treatment with caustic soda at 9.5% or more, the sample aggregated into myrogel particles composed of elements that had become welded together (FIG. 3). This converted cellulose no longer has the characteristic properties of the cellulose of the invention.

In order to retain the special properties of the cellulose of the present invention,
The crystal structure of natural cellulose needs to be maintained. Thus, if a caustic soda solution is used during the alkaline extraction step, a concentration of 9% must not be exceeded.

Example 10: Elimination of minerals Before rehydration, the dried pulp was milled for 10 minutes in a mixing mill equipped with a 1 mm screen. Screening in sieves of 600 μm and 75 μm at the mill exit is 75
One particle fraction with a size of less than μm and a very large fraction between 75 μm and 600 μm was collected. After calcining at 560 ° C. for 8 hours, the ash mass was compared to the initial mass of the sample. This resulted in the amount of ash for each fraction. From 75 μm to 600 μm, a fraction containing 5% inorganic material was isolated, while below 75 μm a fraction containing 12% inorganic material.

Thus, milling followed by screening resulted in a reduced fraction of inorganic material.

Example 11: Elimination of minerals The residue from the purification steps described in Examples 1 to 7 was mixed after a bleaching step at very high speed for 3 minutes in a Waring blender and then filtered through a 25 μm sieve. The effectiveness of such a treatment can be observed with an optical microscope. This is because calcium oxalate crystals have the property of being birefringent when observed under polarized light.
Prior to treatment, a number of crystals were observed between cells at the bottom of the viewing plate, as well as crystals within certain cells. After treatment, crystals were no longer seen between cells at the bottom of the plate.

This example shows that crystals can be eliminated depending on the amount of mixing and washing in a screen of appropriate porosity.

Example 12: Effect of homogenization The suspension from the treatments described in Examples 1 to 7 was a suspension of purified cells composed mainly of cellulose. Microscopic observation showed that the cells were separated to a large or small extent. The suspensions were preheated at 60 ° C. for 1 hour and then passed through a Gaurin homogenizer at a concentration of 2% for a continuous time of 40 MPa and 15 minutes. The temperature rose rapidly from 80 ° C to 100 ° C.

In a homogenizer, the purified suspension is pushed into the tube by a high speed piston and passed through a small diameter orifice,
In it the suspension was subjected to a large pressure drop and then released against an impact ring. The combination of these two phenomena (pressure drop and deceleration impact) resulted in shearing and separation of the cellulose microfibrils. By passing the suspension through the orifice several times, a stable suspension of the separated cellulose microfibrils was obtained. This was evident from light microscopy or electron microscopy. Picture 4
Clearly show the structure interlocked with the cellulose microfibrils that make up the primary wall of beet parenchyma cells. In Photo 5, cellulose microfibrils separated from each other to a large or small extent are seen. This separation effect was a direct result of the homogenization treatment in the Gaurin homogenizer.

The processed sample was a separate microfibril suspension and had the appearance of a gel.

The resulting cellulose had at least 90% primary walls.

 Its crystallinity as observed by X-ray was 33%.

Electron microscope observation showed that the average cross section of the microfibrils was 2
44 nm. They are greater than 7 μm in length and can be 15-20 μm in length.

Example 13: Effect of homogenization (time) The beet pulp was processed as described in Example 3, then mixed at high speed in a Waring blender for 3 minutes and then separated into three parts. The first part was kept intact, the second part was passed through a Gaulin homogenizer six times at 50 MPa, and the third part was passed ten times at 50 MPa. FIG. 6 shows the discrete microfibrils after 10 passes in a Gaurin homogenizer.

These suspensions were studied on a CARRI-MED CSL50 rheometer with a right conical shape. The yield point corresponded to the minimum stress applied to obtain a viscosity directly related to the gel strength. The resulting suspension was also characterized by a viscosity at a shear rate of 57.6 s- ¹ . The results obtained for the three suspensions studied at a concentration of 1% are shown in Table II.

It is clear that the effect of homogenization has resulted in a considerable improvement in rheological properties due to the separation of the cellulose microfibrils. The characteristics of the microfibrils were similar to those of Example 12, except that the percentage of primary walls was 90%.

Example 14: Suspension stability An important feature of the suspension obtained in Example 12 was their ability to produce a stable suspension.

Such a suspension treated according to Example 12 was mixed with 95
Stored for several months at a concentration of 0.1% to 7% without producing a sedimentation volume of less than 10%.

Example 15: Suspension stability A suspension of cellulose microfibrils treated according to Example 12 was treated with a solution of 0.1 M trifluoroacetic acid at 20 ° C for 2 hours.

Analysis of neutral sugars using the corresponding alditoate acetate indicated 95% cellulose. The resulting suspension was not stable.

Trifluoroacetic acid causes preferential hydrolysis of pectin and hemicellulose. Thus, a lack of stability was observed in correlation with the hydrolysis of pectin and hemicellulose.

This example clearly shows that the stability of these suspensions is due to the presence of pectin and hemicellulose bound to cellulose microfibrils.

Example 16: Absorption into Suspension A sample prepared according to Example 12 was oven dried in a flat bottom polyethylene receptacle. 1 at 100 ° C
After 2 hours, a film of dried cellulose was obtained. The film (0.2 g) was macerated in 10 ml of water at room temperature (25 ° C.) and rubbed lightly on a glass. After 30 minutes, a thick paste was obtained. This paste was diluted with water to produce a suspension of cellulose microfibrils having the same properties as the starting suspension.

Example 17: Absorption into suspension Samples prepared according to Example 12 were oven dried in a flat bottom polyethylene receptacle. 1 at 100 ° C
After 2 hours, a film of dried cellulose was obtained. These films were cut into strips and placed in a walling blender with deionized water. After 15 minutes of stirring, the strips collapsed to produce a suspension of cellulose microfibrils having properties similar to those of the starting suspension.

Example 18 (Comparative): Absorption into Suspension A sample prepared according to Example 12 was oven dried at 60 ° C. for 12 hours. A cellulose film treated with trifluoroacetic acid as in Example 15 was obtained. The treated film was then absorbed into a suspension in water.

These samples were difficult to disperse and did not restore the initial properties of the cellulose.

This example demonstrates that uncharged cellulose, which is outside the scope of the present invention, cannot actually be absorbed by the suspension after dehydration without significant loss of its rheological properties.

Example 19: Reactivity Cellulose of the present invention prepared according to Example 12 was purified using Trichoderma reesei CL-847.
Of the enzyme mixture. 810 mg of the cellulose of the invention were absorbed in a suspension in 30 ml of distilled water in a conical flask. Stirring resulted in a homogeneous suspension of cellulose microfibrils, which was equilibrated at 50 ° C. for 15 minutes. An enzyme solution was prepared by dissolving 31.10 mg of the enzyme (corresponding to 25 FPU / g of cellulose) in 15 ml of a pH 4.8 sodium citrate buffer. The solution is added to the reaction medium and this is mixed by horizontal stirring at 50 amplitudes / min.
Incubated at 50 ° C. 4 hours, 8 hours of reaction and
After 12 hours, 3 ml of the homogeneous reaction medium was removed (without changing the concentration) and the enzyme was denatured by heating at 100 ° C. under reflux in a conical flask for 20 minutes, thus stopping the enzyme reaction. It was centrifuged at 1000 g for 10 minutes and then filtered through a microporous cellulose membrane with a pore size of 0.45 μm. Analyzes were performed using HPLC and glucose and cellobiose standards. The cellulose of the invention is rapidly hydrolyzed by the enzyme mixture and after 4 hours of hydrolysis per mg of starting cellulose
0.48 mg, 0.58 mg per 1 mg of starting cellulose after 8 hours of hydrolysis and 1 mg of starting cellulose after 24 hours of hydrolysis
0.85mg reducing sugar (glucose and cellobiose)
Was found to occur.

Example 20: Optimization of process for producing microfibrillated cellulose from beet pulp in an industrial pilot plant Dehydrated beet pulp is 1.5% to 2% by weight based on total liquid
It was absorbed in a suspension in a concentration of ca.

The amount of water required was about 15 (liquid / solid weight ratio)
1 kg of pulp in 15 kg).

The absorption in the suspension was carried out in a tank with stirring. The resulting suspension was heated to 80 C for 2 hours.

The solid fraction of the suspension was then separated from the liquid fraction by passage through a centrifugal dryer having a mesh size of less than 250 μm. The cake was rinsed during centrifugation.

The recovered cake is the same liquid / solid (DM) as above
Absorbed in new 1.5% caustic soda suspension in ratio.

Again, the resulting suspension was heated to 80 ° C. with stirring for 2 hours.

This time, drying was performed again using a finer mesh (25-100 μm), and the cake was rinsed with water.

The cellulose cake was then dried using 33% HCl for 4 hours.
Absorbed in a suspension in 3.5 g / sodium chlorite solution at pH adjusted to ５5. The liquid / solid (D
M) The ratio was again about 15.

The bleached cellulose was then recovered by centrifugation on a 10-30 μm mesh.

The cake was rinsed and centrifuged until a clear filtrate was obtained.

Then, the obtained cellulose is diluted again with water and 3%
A dry matter content of ４4% resulted. The suspension was then passed through a FRYMA mixing mill to break up the cell walls and "prehomogenize" the product.

The ground cellulose was then homogenized in an APV Gaulin homogenizer at a pressure between 450 bar and 550 bar. The product was preheated to a temperature above 95 ° C., so that it was boiling as it passed through the orifice. The purpose was to produce cavitation.

The product underwent 3 to 10 passes, depending on the desired degree of homogenization.

The cellulose was then concentrated to a dry matter content of greater than 35% by passage through a LAROX or CHOQUENET type filter press.

Example 21 Comparative Viscosity of Suspension Before and After Drying Cellulose was prepared as in Example 20.

Samples N # 1 and N # 2 were prepared as follows. Press the cellulose to 40% dry matter and then
% (Sample N ゜ 1) and 85% (sample N ゜ 2).

The two samples are then dried in a conditioning chamber at 20 ° C. and 50% relative humidity and then ground in a coffee grinder for 30 seconds before being absorbed into the suspension in 2 minutes using an Ultra Turrax. (2
% Dry matter).

The control was 2% dry cellulose homogenized using Ultra Turrax for 2 minutes.

After allowing the viscosities of samples N # 1 and N # 2 and the control to stand for 4 hours (due to the thixotropic nature of cellulose), HAAKE, a device for measuring MV _II at a shear rate of 1.8 s ^-1. ) Measured using a VT500 viscometer.

 The following results were obtained.

Viscosity of the control: 25 Pa.s Viscosity of sample N # 1: 25 Pa.s Viscosity of sample N # 2: 22 Pa.s Thus, the cellulose of the present invention when dried to a dry matter of 60% is 100% of its viscosity , And 90% of its viscosity when dried to 85% dry matter.

Thus, the cellulose of the present invention only recovers up to 2% to 20% of the initial viscosity without additives and at least 100 parts by weight of the additive to the cellulose to recover almost all of the initial viscosity. ITT INDUSTRIE needs addition
It is distinguished from the cellulose of S patent EP 120 471.

Example 22: Extraction of potato pulp cellulose (after starch extraction) Purification of potato pulp Potato pulp from which the starch was extracted was absorbed into a suspension in deionized water. For good hydration, intermittent mixing was performed for 45 minutes using a Walling blender mixer equipped with a four blade screw. The suspension was made alkaline by addition of a caustic soda solution of a suitable concentration to obtain a final concentration of 2% by weight of caustic soda and 2.5% by weight of dry matter (both relative to the total liquid). The suspension was heated to 80 ° C. for 2 hours with constant mechanical stirring. After this treatment, it was filtered through a 0.6 mm screen. The solid residue was washed with water until a neutral filtrate was obtained. This alkali treatment was performed once more. The solid residue was washed with water until a neutral filtrate was obtained.

After washing, the solid residue is washed with a mixture of caustic soda and acetic acid.
Sodium chlorite (NaClO ₂ ) solution buffered to pH 4.9
Absorbed in a suspension of 3.4 g / 2.5% in. The solution was heated to 70 ° C. for 3 hours with constant mechanical stirring.
The suspension was then filtered through a stainless steel screen and then rinsed with water to produce a colorless filtrate. A cellulose residue having a dry content of 3% to 5% by weight was obtained by filtration under reduced pressure using a Buchner funnel.

Chemical analysis of the resulting cellulose residue showed 93% glucose. The average degree of polymerization by the viscosity method was on the order of 1000.

Homogenization Homogenization was performed as described in Example 12.

Suspension stability The suspension of microfibrils from potato pulp obtained using the above protocol was stable.

For a dry suspension of 0.3% viscosity, Brookfield: 250 MPa, 30 rpm, needle n ゜ 2 Example 23: Extraction of carrot cellulose 1 kg of 10% DM carrot (ie, 100 g dry matter) was ground. . The ground carrot was absorbed into the suspension in the sodium hydroxide solution to give a mixture of 100 g dry matter in 2 liters of a 2% sodium hydroxide solution.

The suspension was heated to 90 ° C. for 2 hours with mechanical stirring. After this treatment, liquid / solid separation was performed by centrifugation. The solid residue was rinsed. It was then absorbed into a suspension in a 1.5% liquid / solids caustic soda solution.

The mixture was centrifuged again and the solid residue was collected and rinsed.

After homogenization as described in Example 12, a suspension was obtained which was stable in water and had the appearance of a gel.

Although the method of the present invention has been described and illustrated for beet pulp, potato pulp and carrot pulp, it is also applicable to the treatment of soft tissues such as citrus fruits (lemon, grapefruit, mandarin) and most other fruits and vegetables. I can do it.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Vignon Michelle Air France F-38240 Meylan Siman de Beausejour 47 (72) Inventor Morrow Alain France E-27930 Guisian Ville Armeau Fumecon Rue La Foret 2 (72) Inventor Vincent Isabel France F-27000 Evreux Avenue Brian 131 (58) Field studied (Int. Cl. ⁷ , DB name) C08B 1/00

Claims (19)

(57) [Claims] 1. A cellulose comprising at least 80% of primary walls and charged by a carboxylic acid, said cellulose being microfibrillated and charged by galacturonic acid. . 2. The method of claim 1, wherein the primary wall comprises at least about 85% primary walls.
The microfibrillated cellulose according to the above. 3. The microfibrillated cellulose according to claim 1, having a crystallinity of 15% to 50%. 4. The microfibrillated cellulose according to claim 1, comprising microfibrils having a cross section of about 2 nm to about 4 nm. 5. Cellulose, pectin, hemicellulose,
A process for the preparation of microfibrillated cellulose according to claim 1 from primary wall plant pulp, especially beet pulp after saccharose extraction, comprising proteins and inorganic substances, comprising the following steps: (a) pectin and hemicellulose Acidic or basic hydrolysis of the pulp for extraction; (b) recovering the solid residue from the suspension from step (a); (c) under alkaline conditions the cellulose material from step (b) Performing a second extraction of the residue (this step is necessary when step (a) is acidic, and in step (a)
(D is optional if is basic), (d) optionally, a step of recovering the cellulose material residue by separating the suspension from step (c), (e) step (b) or step ( washing the residue from d), (f) optionally bleaching the cellulose material from step (e), (g) recovering the cellulose material by separating the suspension from step (f) (H) diluting the cellulosic material from step (g) in water to obtain 2% to 10% dry matter; (i) homogenizing the cell suspension from step (h) (J) performing step (a) at a temperature of about 60 ° C. to 100 ° C .; (jj) performing at least one alkali extraction step (a) and (c) on the cellulosic material; (B) using a base with a concentration of less than Mixing or milling or high mechanical shearing operations in step (i), followed by passage of the cell suspension through a small diameter orifice, pressure reduction of the suspension by at least 20 MPa and high shear action, followed by high speed deceleration A method for preparing microfibrillated cellulose by subjecting it to impact. 6. The method according to claim 5, wherein step (a) is performed at a temperature of about 70 ° C. to 95 ° C. 7. The method of claim 6, wherein step (a) is performed at a temperature of about 90.degree.
The method described in. 8. The method according to claim 5, wherein each alkali extraction step is performed using a base selected from sodium hydroxide and potassium hydroxide. 9. The method according to claim 5, wherein the concentration of the base used in each alkali extraction step ranges from about 1% to about 6% by weight.
The method according to any one of claims 1 to 4. 10. The method according to claim 5, wherein an additive selected from the group consisting of water-soluble dispersants, suspending agents and thickeners is added to the suspension to be homogenized in step (i). The described method. 11. The method according to claim 5, wherein the homogenizing step (i) is carried out at a temperature of 95 ° C. to 120 ° C., preferably 100 ° C. or higher. 12. The pulp is pulverized before the step (a).
12. A method according to claim 5 or claim 11, wherein the screening retains a fraction having a particle size of about 20m to about 1000m, preferably about 75m to 600m. 13. The process according to claim 5, wherein the bleaching is carried out in step (f), which is associated with an oxidation treatment with ozone or hydrogen peroxide. 14. A method according to claim 5, wherein the bleaching is carried out in step (f) and the treatment is carried out using ozone or hydrogen peroxide.
The method according to any one of claims 1 to 4. 15. After the washing step (e) or the bleaching step (f), the cellulose suspension is appropriately wet-pulverized, and then,
15. The method according to any one of claims 5 to 14, wherein the filtration is carried out with a screen mesh of 20 m to about 75 m. 16. The process according to claim 5, wherein the cellulose obtained from the homogenization step (i) is concentrated. 17. The method of claim 16, wherein the concentration is performed to a dry matter greater than about 50%. 18. The method according to claim 16, wherein the concentration is carried out by pressing, filtering or drying at low temperature and controlled humidity. 19. The method according to claim 5, wherein a high shear operation is performed after the homogenization in step (i).